Direct e-beam (electron-beam) milling has been used conventionally to produce grayscale features in a substrate by directing an electron beam towards the substrate in a scanning pattern and either modulating the intensity of the electron beam or the scan rate across the substrate such that a grayscale pattern is produced in the substrate as grayscale features. However, direct e-beam writing is both slow and costly, and also the precision of the grayscale features (e.g., the height of each step of the grayscale features) is based on how precisely the scan rate and/or the intensity of the e-beam are set. The use of lower intensities and commensurately lower scan rates may improve the precision with which these parameters may be controlled, but at a cost in throughput.
Given these potential disadvantages of direct e-beam milling, an alternative method of producing precise grayscale features in a substrate with a reduced time to completion and a reduced cost may be desirable. Improved precision in the height of these grayscale features (e.g., the overall height and the height of each step) may also be desirable. Three dimensional (grayscale) lithography may offer such an alternative approach to forming grayscale features. The present invention involves the use of a laser beam writer for grayscale lithographic applications.